Method of producing volatile metals from their sulphides



Patented Aug. 7, 19128.'

PATENT @FHQE.

HENNIN G GUSTAV FLODIN,

OF ROS LAGS-NASBY, AND EMIL GUSTAF 'IORVALD GUS- TAFSSON, OF STOCKHOLM, SWEDEN; SAID HENNING GUSTAV FLODIN ASSIGNOB TO HARRY BBOADY, F STOCKHOLM, SWEDEN.

METHOD OF PRODUQIN G VOLATILE METALS FROM THEIR SI ILPHIDES.

No Drawing.

The present invention relates to a method of producing such metals from their sulphides, which are capable of being liberated from their sulphides by iron, such as zinc, lead and silver, while using metallic iron as sulphur-binding agent. Our new process is especially suitable for producing zinc from zinc sulphide, for instance from complex zinc ores, but it may also be applied for provducing for instance lead from lead sulphide.

It has been previously proposed, for instance for the product-ion of zinc out of zinc blende, to heat the ore together with molten iron, but this process has not met with any success, inasmuch as it has been impossible to cause the conversion to take place in'even thus obtained is roasted, the ferric oxide being then reduced, and the iron'obtained again used as a sulphur-binding agent, It has been found, however, that a mixtureof the charge thus produced outside the furnace is not suflicient to secure, from a tech nical point of view, a good yield of the zinc out of the zinc ore, becau'e'the mixture within the furnace will only too readily disintegrate into its constituents. before the process of conversion is completed.

Accordingto anotherproposal for producing zinc from zinc .sulphide in retort furnaces a mixture of unroasted Zinc sulphide with iron and with carbonaceous material suitable for coking is formed into briquettes, which! are distilled under such conditions that the briquettes are first coked into coherent masses, and 'final'lv, the zinc is reduced and volatilized, while the resulting iron sulphide is retained in minute par ticles throughout the coke, thus preventing 'theretorts from being destroyed by the iron sulphide. Nor has this process, however, gained any practical use as the conversion between thematerials is very incomplete on account of the great quantity of carbona- Application filed April: 10, 1924. Serial No. 705,531.

ceous material which necessarily must be added.

. The main object of our present invention is to provide a method of the type described in which the reaction between the sulphide and the iron will be substantially complete and a good yield-of the metal from the sulphide material will be obtained.

Another object of our invention is to provide a method of the type described in which the metal is distilled andcondensed and the condensation takes place without the diiiiculties arising in electric zinc processes hitherto employed, permitting of producing a metal of extreme pureness.

Still another object of our invention is to provide a method of the type described in which certain steps are taken for the purpose'of carrying out.the reaction in most suitable manner so as further to increase the output.

lVith these and other objects in view our invention consists essentially in heating in a closed electric furnace, i. e. a furnace the interior of which is held free from air, a charge of solidified briquettes of a mixture of a finely divided "material containing a sulphide of a metal capable of being liberated. from the sulphide by iron, with metallic iron in finely divided state. said charge be ing of such a nature that in the briquettes the particles of the materials are in intimate contact with one another and fixed as regards their relative positions. said charge being heated to such a temperature that the sulphur combined with the metal is given off to the iron and the metal is liberated. v

The expression briquettes is in that connection understood to comprise not only what is usually termed briquettes, that is to say bodies of a more or less regular form, but also other bodies of more or less irregular form, provided, however, that each body eon:ists of several small particles of sulphideore and iron. Further the size of such bodies may vary-from that of a grain of sand to larger lumps.

F or the heating any electric furnace may be used, but furnaces of the resistance type,

for instance electrode furnaces in which heat is developed by electric resistance in the slag, are to be preferred.

' According to a preferred embodiment of our new method applied to the production of zinc fromv zinc sulphide, ore or materlal containing zinc sulphide, such as zinc blende, complex zinc ore or the like, is finely crushed and intimately mixed with finely divided metallic iron, preferably 'in the form of spongy iron; althoughalso iroir in the form of pig-iron, broken cast iron or the like as 10 well as ferro-alloys may be used, provided the iron'has-qthe requisite degree of fineness which-may be -effected by crushing, gr1nd1ng, trituration or any similar process. By forming the spongy iron from finely div ded ferric oxides, such as concentrates of non ore, the spongy iron may be obtained direct-- ly in a sufliciently fine-grained state by car-' rying out the reduction in a suitable man-.

- her, for instance in a revolving furnace, and

in such cases crushing or grmdingof the spongy iron is, of course, not necessary. This mixture is transformed into briquettes or equivalent bodies by any known method. When spongy iron is used as a sulphurbinding agent, the comparatiyely soft particles of. the spongy iron will at the same time act as a binder in the briquetting process, butwhen iron in other form is used, a

,particles in the briquettes. will remain inintimate contact with one another and fixed' in their relative positions, and no separaprior to the reaction. In heating to the retion of the ,ore and iron particles will 'setin action temperature which, as a. rule, may lie below the melting temperature of the materials, one may thus rest assured that, on

properly adapting the admixture of iron, the

. suitable quantity of iron required to bind the sulphur of thesulphide combined with the zinc will be present everywhere, a libera-.

tion of the zinc as complete as poss'ible'being thus attained. The zinc may then, subect to its boiling point, either escape in a gaseous state atonce, orbe caused to do so by further heating of the charge.

-In several cases it may be preferable to cause the material to melt and to parry out the heating and melting withthe briquettes floating on top of a slag bath in the furnace. If required, suitable fluxes should then be added to the charge in a finely divided state, or be introduced into the furnace directly, so that a slag suitable for carrying out the process is obtained in the furnace" If "the briquettes sink entirely underneath the surface of the slag bath prior to the reaction of the metal sulphidewith the iron, the briquettes .will easily burst by the violent development of gaseous metal tak-- ing place on the rapid heating in the slag bath. The homogeneousness of the briquettes willthen be destroyed, which is a very great drawback for a complete conversion. By admixing suitable substances in the briquettes or with the same, for mstance lime, dolomite, quartz, clay or the like, said substances being accommodated to the gangue of the ore, or by suitably adapting the degree of pressing of the briquettes,

the briquettesmay be given such a s ecific gravity relative tothe slag that they W111 float on top of the slag, which latter may at the same tlme be given such a toughness as to aid in preventing the briquettes from sinking below the surface ofthe slag bath.

Tlie zinc gases leaving the furnace are condensed inany suitable manner and apparatus, or may be directly burnt to zinc oxide which may be used asdye stuff or for anyother purpose.

Instead of mixingfinely divided sulphide, ore of 'the metal in question, for instance zinc, and finely divided iron, that is to say,v instead of fine-crushing the ore and the iron separately, it may be preferable to effect said fine-crushing simultaneously and in the. same apparatus with both the iron and the ore, the sharp-edged particles of the ore thereby aiding in the grinding and crushing of the iron, especially in case of using quartziferous ores;

The method according to the invention is obviously adaptable also for producing -metal capable of being liberated from: its

sulphide from material or ore containing the-metal in the form of sulphide as well as of oxide. Thequantity of iron should then [be proportioned to the quantity of sulphur to be combined, in addition to which a req uisite quantity of carbon should .be added to the mixture before transforming into briquettes in order also to transfer the oxide into metal, a suitable quantity of flux being also added, if desired. If the carbon is added in the form of liquid carbonaceous substances, such as tar, molasses, sulphite waste liquor or the like, a very accuratedistribu tion of the carbon is obtained in the briquettes or the pieces of material, whilevat the same time the liquid substance also serves as a binding agent. I

In a number of ores requiring so high a heating temperature that the charge is 4 caused to melt, it maybe preferable to expel the metal or metals combined with sulphur and that or those combinedwith oxy- 7 gen 1n different stages. In such a case, the ore-iron mixture in the'form 'of pieces or briquettes is first heated to such a temperature that the metal combined with sulphur is liberated, after which the remainder is heat; ed, after having been mixed with carbon and, if required, with flux, in the same or another furnace, to the temperature required to reduce the oxides. This latter. mixture may preferably also be transformed into briquettes before heating.-

If the material or'the ore treated, such'as complex zinc ore, contains, in addition to sulphide of zinc, one or more sulphides of metals which also are capable of being liberated from their sulphides by iron but which are comparatively more difficult to volatilize than zinc, such as lead and silver, these latter sulphides are also reacted onby the iron causing the metal or metals to be liberated. As a relatively low temperature is suflicient to expel the volatile zinc, a very small portion of'the comparatively nonvolatile metals is transformed into a gaseous state, whereas the major portion may be accumulated in the form of molten metal at the bottom of the furnace, whence the molten metal or metals are tapped ofl' and utilized. Consequently, the gases escaping from. the furnace will. by carrying out the process at a relatively low temperature, contain vapours of zinc of a high degree of pureness, and the products obtained in condensing the gases or treating them in any other way will be much purer than in the electric methods hitherto .eniployed. -In order .to draw off both kinds of metal as completely as possible, it is preferable to in corporate in the briquettessogreat a quantity of iron that all metals will be liberated.

In order to bring about a complete conversion between the metal sulphides and the iron, it is, as mentioned before, of the utmost importance that the two materials on being heated are brought into contactwith one another as intimately as possible. According to a modified embodiment of our new method, this object may be attained by producing the metallic iron in the briquettes directly, before they are heated to the temperature required for the reaction between the metal sulphides and the iron. In such a case, the finely divided sulphide ore is mixed,instead of with iron, with oxide of iron of some kind or other.'such as ironore concentrates, and with carbon proportioned to its reduction, and to the reduction of any metal oxide that may be present in the sulphide ore. the iron oxide and the carbon being both finely divided, whereupon the mixture. is transformed into briquettes which are then heated to the proper temperature, the iron oxide being then converted into iron, while the carbon absorbs the oxygen andescapes in a gaseous state as carbon monoxide or carbon dioxide or both. By this means the briquettes will then contain metallic iron in the form of spongy iron finely divided and intimately mixed with the sulphide material. The briquettes are then treated as set forth above.

If the production of spongy iron is effected in the same furnace wherein the distillation is taking place, the furnace should be provided with means preventing the gases generated in the production of the spongy iron from entering the condensers for the volatile metal gases,the former gases being drawn oft separately.

In the reaction the iron is combined with the sulphur of the metal sulphide as sulphidefof iron and accumulates at the bottom of the furnace, perhaps on top of any separated metalless volatile than" the metal to be produced, such as lead and silver. The sulphide of iron may of course be tapped off and be used as such for any purpose, for instance by treating the same with air or with some other gascontaining oxygen, such as steam, which gas may be heated, or not, for the oxidation of the sulphur as well as of the iron, the sulphur being then transformed .into sulphurous acid and somewhat to sulphuric anhydride and the iron being oxi- 'dized,to ferrous oxide or ferric oxide. The treatment may for'instance be carried out. in such a manner that air or gas under pressure is car sed-to meet and finely divide the flow of su phide of iron (matte), or is blown through the latter in converters or the like. The oxidesof iron may be restored by reduction to a metallic state in the form of spongy iron, pig iron or the like, in order tobe used anew as a sulphur-binding agent in the process or for other purposes. If the ore, in addition to sulphide of a metal capable of being liberated from the sulphide by iron, alsoycontains sulphide of a metal not r having this property, for instance if the ore is cupriferous, copper will be found in the form of sulphide in the sulphide of iron formed during the reaction and may beextracted in known manner from this matte in 'some form or other. If the iron is caused to circulate in the process. a steady concen-. tration of the copper contents of this iron will take place. Thus, after circulation for some time, the sulphides of iron and the oxides of iron or the iron respectively. may in known manner advantageously be treated for the recovery of copper, even if the initialsulphide ore has a low percentage of copper, Should the ore also contain silyer, the cupriferous matte will also contain some silver and, of coursefiin higher degree if the sulphide of iron or the iron is circulated.

If in addition to metal or metals capable of being liberated from the sulphide by iron, the material or the ore also contains iron 'pyrites, the one sulphur atom of the pyrites will be dissociated on the charge being heated. ,If the temperature is sufficiently high, nearly all of this sulphur will combine with the iron in the charge; otherwise the 7 a portion of the latter.

. gas outletof'the furnace. Him the latter case no zinc vapours are present in the furaltcred in a gaseous state to the condensers,

I which again will result in drawbacks. 'The major part of the sulphur, however, com-' I bines with the iron, if the temperature is sulficiently high, and consequently consumes Thus the charge must contain a suflicient quantity of iron in order also to-bind the free sulphur of iron pyrites that may be present in the material. In order to avoid this consumption of metallic iron, it ispreferable, at least if the-content of iron pyrites is considerable, to subject the ore prior to its admixture with the iron to a preliminary heating to about 700 C., that is to say-to the temperature at which the one sulphur atomnofthe iron "pyrite s is expelled. This sulphur may then be recovered in known manner. v

The method according to the invention offers very great advantages as compared withthe methods hitherto used in practice.

are diflicult to roast, if the-roasting is at 40 In the latter methods only roasted ores could be used to advantage, whereas, according to the present invention, our novel ing of the sulphide ores iscthus. eliminated,-

which is of great importance particularly with respect to the complex ZlIlC ores that all possible to accomplish, and on roasting lose a great portion of their metal contents on account of metal gases escap ng w1th the roast gases.

Another very great-advantage in the pres entmethod results from the fact that practical'ly no gas, or at any rate an exceedingly small amount; of gas, is obtained in addition 7 to the -metal; gases. If by reactions in the furnace chamber gases other than the metal gases are also produced, the condensation 1s rendered very difiicultand roducts will be obtainedv that are partly 0 an" undesirable character." For exampl in the production of zinc from roasted zin ores according. to ,the methods known hitherto, great quantities of gas (carbon monoxide and carbon dioxide) will form on the oxide of the ore be ing reduced with carbon, such gases involvlngvery great drawbacks in the condensa-' tion of the zinc gases, and resulting in that the zinc is obtained only partly in the form of so-called fluid zinc;while the remainder forms so-called poussieres (blue powder).

I Particularly in' the production of zinc m an electric furnace such production or blue powder is considerable, in "that 30% or more of the zinc is obtained in this form. Suchpowder must then be transferred into fluid zinc at a considerable cost, or, it must be subjected to renewed treatment in the process. On the 7 contrary, when using the method according fnace chamber, the sulphur will escape un- "to the invention, the condensation will take place without such difliculties, whereby the capacity of the condensing apparatus is correspondingly increased, and practically the. Z5 whole quantity of zinc is obtainedas' fluid zinc, in addition to which such zinc can be. obtained ina high degree of pureness. "If the sulphide ore used also contains metal oxide, then, obviously, when said oxide is. reduced with carbon, carbon monoxide will be produced also. in ouraproces's, but the amount of gas will nevertheless always be smaller than in producing the metal solely out of oxide. i 35 The invention is not restricted to the material,cores, metals or substances above enui merated as examples, but comprisesall materi'als, ores, metals and substances fulfilling the conditions set forth. 'It is also of no'eonsequenee, whether the ore or the material contains one or more sulphides of one or more metals not having the property of being capable of being liberated from the sulphide by iron, provided only that said ore or material contains some sulphide of a metal having such a property. a I

en in this description and the appending c aims ore is spoken of, this word is to be understood also to cover all other materials containing one or more sulphide'sof metalormetals capable of being liberated fromlthe sulphide by iron and, perhapsralso" sulphides of other metals, such as products, wastes or the like obtained from other proc v esses.

What we claim as new and desire to, secure by Letters Patent of the United States of America is 1. A method of producing metals from 110. their sulphides, comprising heating. in-a closedelectric furnace a charge of solidified briquettes of a mixture. of a finely dividedmaterial containing a sulphide of a metal capable ofbeing liberated from the sulphide by iron, with metallic iron in a finely divided state, said chargebeing'of sucha nature that in the briquettes the particles of the materials are-in intimate contact withone another and fixed .as regards their rela- 12o tive positions, said charge being heated to such a temperature that the sulphur com-f bined; with the metal isgivenofi to the iron and the metal is liberated. 4 f i I V 2. A method of producing metals from 125. their sulphides, comprising mixing .a finely divided. material containing asulphideof a metal, capable ofbeing liberatedfrom the sulphide by iron, with metallic iron'in. a. fine- 13 divided state,"an d spongy iron as a bind 1 ging agent, transforming saidrmixture into A briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards. their relative positions, and heating said briquettes in a closed electric furnace to such a temperature that the sulphur combined with the metal is given off to the iron and the metal is liberated.

their sulphides, comprising mixing a finely 3. A method of producing metals from their sulphides, comprising mixing a. finely divided material containing a sulphide ofa volatile metal, capable ot being liberated from the sulphide by iron, with metallic iron in a' finely divided state, transforming said mixture into briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards their relative positions, and heating said briquettes in a, closed electric furnace to such a temperature that the sulphur'combined with the metal is given off to the iron and the metal is liberated and distilled.

4. A method of producing metals from their sulphides, comprising mixing a finely divided material containing a sulphide of a volatile "metal, capable of being liberated from the sulphide by iron, with metallic iron in a finely divided state, transforming said mixture into briquettes of such anature that heating and melting same whilst floating on i a slag bath with heat at least in part developed by electric resistance in the slag to such a temperature that the sulphur combined with the metal is given olf to the iron and the metal is liberated.

7. A method of producing metals from their sulphides, comprising mixinga finely divided material containing a sulphide of a metal, capable of being'liberated from the sulphide by iron, with metallic iron in a finely div ded state, transforming said IIllX ture into briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards their relative positions, feeding said briquettes into a closed electric furnace together with a suitable slag-forming material of such a nature that the specific gravity of the molten slag will be greater than that of the briquettes, and heating and melting the charge by means of electric current whilst floating on said slag bath to such a temperature that the sulphur combined with the metal is given off to the iron and the metal is liberated,

8. A method of producing metals from 4 their sulphides, comprising mixing a finely divided material containing a sulphide of a metal, capable of being liberated from the sulphide by iron, with metallic iron in a finely divided state, transforming said mixture into briquettes of such a nature that the particles of the materials are in intimate contact-with one another and fixed as regards their relative positions, feeding said "briquettes into a closed electric furfiacetodivided material containing a sulphide of a r metal, capable of 'being liberated from the sulphide by iron, with metallic iron in a finely divided state, transforming said mixture into briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards their relative positions, feeding said briquettes into a closed electric furnace, heating and melting same by means of electric current whilst floating on la slag bath to such a temperature that the sulphur combihed with the metal is given 01f to the iron'a-nd the metal is liberated.

6. A method of producing metals from divided material containing a sulphide of a metal, capable of being liberated from the sulphide by iron, with metallic iron in a finely divided state, transformingsaid mixture into briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards their relative positions, feeding said gether with a suitable slag-forming material of such a nature that the slag formed during the melting process will be given such a toughness that it will aid in preventing the briquettes from sinkingbelow the surface of the slag bath prior to the reaction between 4 the metal sulphide and the iron, heating and melting the charge by means of electric current whilst floating on said slag bath to such a temperature that the sulphur combined with the metal is given off to the iron and the metal is liberated.

9. A method of producing metals from their sulphides, comprising mixing a finelydivided material containing sulphide of a metal, capable of being liberated from the sulphide by iron and oxide of said metal,

with metallic iron and carbonaceous material 'both in a finely divided state, transforming said mixture into briquettes of such a nature that the particles of the materials are in intimate contact withone another and fixed as regards their relative positions, and heating said briquettes in a closedelectric furnace to such a temperature that the sulphur and oxygen combined with the metal is given off to the iron and to the carbon respectively and briquettes into a closed electric furnace, and the metal is liberated.

by iron, with metallic iron, exposing said 10. A method of producing metals from their. sulphides, comprising mixing a material containing a sulphide of a metal, capable of being liberated from the sulphide mixture to a fine-crushing process, transforming said mixture into briquettes of such a nature that the particles of the materials are in intimate contact with one another and fixed as regards their relative positions, and heating said briquettes in a closed electric furnace to such a temperature'that.thesulphur combined Withthe metal is given off to the iron and the metal is liberated.

,11. A method of producing metals from their sulphides, comprising mixing a finel divided material containing sulphide of a metal, capable of being liberated from the quettes of'such a nature that the particles of the materials are in intimate contact'with one another and fixed as re ards their relative positions, heating' sai' briquettes in a closed electric furnace to such a temperature using the metallic iron thus produced again in the process until the matte contains the. desired percentage of said other metal.

' In testimony whereof We aflix our signatures. x a

, HENNING tusTAv FLODIN.

EMU. GUSTAF TORVALD GUSTAFSSQN. 

